I’m glad that you’ve finally got it working! Under the circumstances (history of mediocre academic performance, family business that may need your help intermittently), it seems to me that you can get your major at a nearby UMass (Lowell, Boston, or Dartmouth). You could start off there for basically the price of in-state tuition and a commute, and if things go well, you could consider transferring to UMass Amherst, or anywhere else that you want.
Look at it this way. You can start off at a UMass for 17K/yr plus commuting costs, or you could wind up spending a ton more to go to a private college that has little advantage over UMass for about 50-60K more/year. It doesn’t sound as if your family would qualify for fin aid, unless they are grossly under-declaring the income from the restaurant. Couldn’t that extra 50K/yr be put toward better use?
Two semesters at the local UMass, then transfer to UMass Amherst, which is a great school, fantastic bargain for in-state.